There are a variety of instruments that are designed to interact with a patient through electrodes applied to the patient's skin. Several examples include electrocardiograph (ECG), electroencephalograph (EEG), and electromyograph (EMG) instruments. Such instruments operate by making electrical connections with the skin, through which electrical signals can pass.
The quality of the contact between the electrode and the skin can greatly impact the quality of the signal obtained from the patient. Several factors can influence the quality of the connection. A major factor is whether appropriate skin preparation steps are taken prior to the connection of the electrode. A skin preparation process may include shaving the skin surface to remove hairs, cleaning the skin surface, and lightly abrading the skin surface to remove dead skin cells. The electrode itself can also influence the quality of the connection. For example, some types of electrodes can become dried out over time. The electrical connection quality can also be reduced if a conductive gel is not applied between the skin and certain types of electrodes that require such a gel. If a non-conductive gel, such as a type used for ultrasound procedures, is inadvertently used, the quality of the electrical connection can be reduced.
Even if electrodes appear to be well connected to the skin and skin preparation has been properly done, the quality of the electrical contact can still be relatively poor for some patients. A visual or physical inspection of the electrodes is not adequate to determine the quality of the connection. A poor electrical connection can result in increased susceptibility to interference, or complete inability of the instrument to interact with the patient in the intended manner.